It is likely that, in future, new battery systems on which very high demands in terms of reliability are placed will increasingly be used both in static applications, for example in wind power installations, and in vehicles such as hybrid and electric vehicles. The reason behind said high demands is that failure of the battery can lead to failure of the entire system or even to a safety-related problem. Thus, in wind power installations, for example, batteries are used in order to protect the installation against inadmissible operating states in a high wind by virtue of rotor blade adjustment.
Usually nowadays, lithium ion batteries involve the voltage of each cell being monitored individually, in order to be able to protect said cells from overloading during the charging process. Typically, a non-generic integrated circuit having multiplexers and analog/digital converters is used for this purpose, which integrated circuit communicates with a control unit. This solution is complex and expensive.
FIG. 1 illustrates the principle of such monitoring of an individual cell in accordance with the prior art. A battery management unit 10 comprises an integrated circuit 14 that is electrically connected to each of the battery cells 12a, 12b, . . . 12n of a battery. The integrated circuit 14 comprises a multiplexer and an analog/digital converter and is connected to a control unit 18 by way of a communication bus 16.
A charging circuit for battery cells is known from DE 10 2006 033 171 A1, in which in each case a bypass is assigned to the individual battery cells, via which bypass a charging current is conducted to the individual battery cells depending on the charging state thereof. The charging process can be terminated if all of the battery cells or a predetermined number of battery cells have reached the maximum permissible voltage value thereof.